CA1244865A - Insulator for and method of installing electric resistance heater - Google Patents
Insulator for and method of installing electric resistance heaterInfo
- Publication number
- CA1244865A CA1244865A CA000490314A CA490314A CA1244865A CA 1244865 A CA1244865 A CA 1244865A CA 000490314 A CA000490314 A CA 000490314A CA 490314 A CA490314 A CA 490314A CA 1244865 A CA1244865 A CA 1244865A
- Authority
- CA
- Canada
- Prior art keywords
- insulator
- coil
- heating element
- notch
- convolutions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
- H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
- H05B3/32—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulators on a metallic frame
Landscapes
- Resistance Heating (AREA)
Abstract
Abstract of the Disclosure An insulator for a coil-type electric resistance heater is disclosed in which the insulator has inclined side faces forming the outer end of the insulator angling inwardly toward one another with side notches in the insulator at the base of the inclined side faces and a central notch in the outer end of the insulator between the two inclined side faces. The distance between the center notch and the outer ends of the inclined side faces is less than the spacing of the adjacent convolutions of the heater element coils so that upon aligning one convolution with the central notch and upon moving the insulator inwardly toward the axis of the coil, the one convolution will be received in the center notch and the adjacent convolutions will be wedgingly engaged by the side faces of the insulator so as to resiliently spread the convolutions such that the adjacent convolutions will snap into the side notches.
A method of installing an electrical resistance heater on a plurality of insulators is disclosed.
A method of installing an electrical resistance heater on a plurality of insulators is disclosed.
Description
~2~ 5 Bac~_ound of the Invention This invention relates to electrical resistance heaters, an~ more particularly to such heaters in which the heating element is formed of electrical resistance heating wire, of nichrome or the like, and even more particularly in which the heating element is formPd in a helical coil and in which the neating element is supported on a ~ame or the lik~ by mean~ of ceramic-like insulators. Such heating element~ find a wide range of applications, such as in electric clotheg dryer~, resistance neating systems for residential and in commercial heating and ventilating systems.
Heretofore, electrical resistance heating elements, such as descriDed above, were mounted on a ~etal frame and were carried by ceramic electrical insulat~rs thereby to electrically isolate the heating element from ~he frame. As shown in U.S.
patent 3,697,727, these insulators were typically hollow collars or bushings tnrough which the coiled elec~ric resistance heating element was inserted. Howeve~, it has been found that these ring-like insulator collars were not entirely desirable because air flow through ~he collars was ~omewhat limited and thu~
increased significantly the surface temperatur~ of the electric resistance heating element within ~he collar several hundred degrees Fahrenheit above the temperature of the heating element exposed to air flow thereover. Thi~ increased temperature of the heating element within the collars deleteriously affected ~ervice life of the neating e}ement because of increased rates of oxidation of the heating element wireO Further, the insulator busnings did no~ securely fasten or anchor the heating coils and, i5 during repeated firing and unfiring of the heating element, the coils would slide on the collars and abrade the heating element, weakening it and leading to reduced service life of the heating coil.
Still further, the requirement of having to use ~olid circular insulator collars required more t~me to assemble the heating element because the insulator collars had ~o be threaded onto the continuous length of the heating element.
Additionally, as is illustrated in the above-noted U.SO
patent 3,697,727, the heating element was typically of helical coil construction from one end to the other with the heating coil being formed in a generally serpentine arrangement ~ith the parallel portions of the hea~ing elemen~ constituting runs and with the portions of the heating element inte~connecting adjacent runs being referred to as turnarounds. Typically, ~uch a continuous, coiled heating element is installed in an air duct or the like through which air may be ~orceably circulated thereby to transfer heat from the heating element to the air flowing therethrough. This compact, serpentine design of the heating element is desirable because it maximizes circulation of the air over the heating element and thus enhances heat transer to the air. However, the lengths o~ the heating element runs which are freely supported ~e~ween the insulators tend to lose strength wnen heated or fired and, over time, ~he weight of the coi~ed helical heating element hanging between the insuIator~ could cause the heating elements to sag. This sagying is particularly undesirable because if the heating el~ment ~ags beyond a certain degree because the heating element may break ox may contact the 8~5 sidewalls of the duct within which it i8 installed or the frame carrying the heating element thus shorting out the heating element. Therefore, there has been a long~tanding need to support the heating element so as to eliminate or lessen the tendency of the unsupported lengths of a coiled heating element ~o sag.
The coassigned U~S. patent 4,472,624 represents an important step in the art in that the insulator di~closed therein securely engaged three adjacent convolutions of the heating coil witn the center of these convolutions displaced in lateral direction from the other two relative to the longitudinal centerline of the coil. This positively held the coil from moving relative to tne insulator and minimized sagging of the coil. ~owever, insertion o~ the coils on the insulators was a time-consuming task that reguired hand labor with its attendant high labor costs.
Reference made to such U.S. patents as 1,844,678,
Heretofore, electrical resistance heating elements, such as descriDed above, were mounted on a ~etal frame and were carried by ceramic electrical insulat~rs thereby to electrically isolate the heating element from ~he frame. As shown in U.S.
patent 3,697,727, these insulators were typically hollow collars or bushings tnrough which the coiled elec~ric resistance heating element was inserted. Howeve~, it has been found that these ring-like insulator collars were not entirely desirable because air flow through ~he collars was ~omewhat limited and thu~
increased significantly the surface temperatur~ of the electric resistance heating element within ~he collar several hundred degrees Fahrenheit above the temperature of the heating element exposed to air flow thereover. Thi~ increased temperature of the heating element within the collars deleteriously affected ~ervice life of the neating e}ement because of increased rates of oxidation of the heating element wireO Further, the insulator busnings did no~ securely fasten or anchor the heating coils and, i5 during repeated firing and unfiring of the heating element, the coils would slide on the collars and abrade the heating element, weakening it and leading to reduced service life of the heating coil.
Still further, the requirement of having to use ~olid circular insulator collars required more t~me to assemble the heating element because the insulator collars had ~o be threaded onto the continuous length of the heating element.
Additionally, as is illustrated in the above-noted U.SO
patent 3,697,727, the heating element was typically of helical coil construction from one end to the other with the heating coil being formed in a generally serpentine arrangement ~ith the parallel portions of the hea~ing elemen~ constituting runs and with the portions of the heating element inte~connecting adjacent runs being referred to as turnarounds. Typically, ~uch a continuous, coiled heating element is installed in an air duct or the like through which air may be ~orceably circulated thereby to transfer heat from the heating element to the air flowing therethrough. This compact, serpentine design of the heating element is desirable because it maximizes circulation of the air over the heating element and thus enhances heat transer to the air. However, the lengths o~ the heating element runs which are freely supported ~e~ween the insulators tend to lose strength wnen heated or fired and, over time, ~he weight of the coi~ed helical heating element hanging between the insuIator~ could cause the heating elements to sag. This sagying is particularly undesirable because if the heating el~ment ~ags beyond a certain degree because the heating element may break ox may contact the 8~5 sidewalls of the duct within which it i8 installed or the frame carrying the heating element thus shorting out the heating element. Therefore, there has been a long~tanding need to support the heating element so as to eliminate or lessen the tendency of the unsupported lengths of a coiled heating element ~o sag.
The coassigned U~S. patent 4,472,624 represents an important step in the art in that the insulator di~closed therein securely engaged three adjacent convolutions of the heating coil witn the center of these convolutions displaced in lateral direction from the other two relative to the longitudinal centerline of the coil. This positively held the coil from moving relative to tne insulator and minimized sagging of the coil. ~owever, insertion o~ the coils on the insulators was a time-consuming task that reguired hand labor with its attendant high labor costs.
Reference made to such U.S. patents as 1,844,678,
2,g21,172, 3,016,441, 3,358,074, 3,641,312, 3,770,939, 3,846,619,
3,890,487 and U.S. Design Patent 262,285 ~or prior art references in the same general field as the present invention.
Among the several objects and ~eatur~ of this disclosure may be noted tne provision of an insulator for an electrical resistance heater in which the insulators contact three adjacent convolutions of the helical coiled heating element at only localizea points therearound thereby to permit air circulation to flow freely over the convolutions supported by the insulators;
8~
The provision of such an insula~or in which the heating element may be ~ormed to i~s desired configuration and readily applied to the insulators already installed on t.he frame for the heating element;
The provision of such an insulator in which the heating cQil may be readily installed on the heating coil in such manner as to effect substantial labor ~avings in assembly of the heating element and, at least in certain instance~, to facilitate the automated installation of the heating coil~ on the insulators;
The provision of such an insulator which minimizes stretching of the heating element coil as the latter i~ installed on the insula~ors, and yet which in~ures that the heating coil is locked in place on the insulator~
The pravision of sucb an insulator which permits the ready field repair of the heating elemen~, even after ~he heating element has been ~ired, without undue breakage o~ the heating element;
The provision of such an insulator wbich support~ the runs of the heating element in 6uch manner as to lessen the tendency of:the heating element ~o sag; and The provision of such an insulator which is of simple and rugged construction, which i~ easy ~o assembly, which requires less labor to manu~acture, which has a longer service life, and which is more readily field repairable than prior heating elements. ~
Other objects and features of this invention will be in part poin~ed out and in paFt apparent hereinafter.
. - 5 -Briefly stated, an electrical resis~ance heater typically has an elongate wire heating elemen~ of generally helical coil shape. The helical coil has a coil axiz and a plurality of convolutions spaced at ~ubstantially equal intervals along the coil axis. The heater further has a frame and a plurality of electrical insula~ors for supporting the heating element on the frame. Each o~ the insula~ors has a unitary body of a suitable electrical insulative material. The body has a first and a second side facing in generally opposite directions.
Tne insulator includes means for mounting ~he insulator body with respect to the frame such that the first and second sides are generally in line with the coil axis. The insulator body further has a side notch in each of it~ above-mentioned ~r~t and second sides, with each of the side notches extending generally inwardly toward the center of the insulator body~ Further, at lea~t a portion of the first and second sides of the insulator body is spaced outwardly from the insulator body mounting means, and these portions angle inwardly so as to con~titute a pair of outer ~aces converging toward one another. The insulator ~urther has an outer end between the angled outer faces, with ths outer end of the insulator body having a center notch therein extending inwardly toward the moun~ing means. The ends of the in~ulator body between the outer ends of each of the angled outer faces and the outer end of its adjacent center no~ch face has a wid~h less than the axial spacing between the convolutions of the coil along the coil. ~his permits the ends of the insulator and the coil heating element to be assembLed by disposing the insulator relative to the coil with one convolution ~ub~tantially in register with the center notch, and with adjacent convolutions on Opposite sides of this one convolution being engageable with a respective angled outer face of the insulator body. By moving the insulator and coil toward one another, the one convolution i~
received within the center notch, and ~he adjacent convolutions are weagingly spread outwardly away from the one convolution generally along the coil axis by engagement with their respective anglea outer faces of the insulator body unti~ the adjacent convolutions are in register with and snap into their respective side notches. In this manner, the side notche~ positively hold their respective coil convolutions again~t movement toward and away from the insulator body and such that the cen~er notch hol~s its respec~ive coil convolutions against movement along the coil axis.
Further, this disclosure includes a method of installing such a coil-type heating element on an insulator, generally as above-described, in which one heating element convolution is inserted into the center notch of the insulator, and in which adjacent convolutions are brought into contact with the angled outer faces of the insulator body. Then, the heating element coil is shoved onto the insulator such that the outer angled faces of the insulator wedgingly spread the adjacent convolutions outwardly relative to the one convolution received in the center notch until such time as the adjacent convolutions are received in the side notches such that the side notches prevent movement o the heating coil toward and away from the insulator, and ~uch that the convolution received in the center notch permits movemen~ of the heating elemen~ in the direction o~ the axis of the heating element coil.
3 6;5 In the accompanying drawings which illustrate embodiments of the invention;
FIG. 1 is a top plan view of an elect~ical resistance heater assembly having a plurality of runs of a coiled heating element supported on a frame by a plurality of in~ulators;
FIG. 2 is a side elevational view of FIG. 1, showing the insulator of FIG. 8;
FIG. 3 is a front elevationa~ view o~ a ~irs~ insulator embodying the present invention;
FIG. 4 is a side elevational view of the insulator of FIG. 3;
FIG. 5 is an enlarged view of the lower portion of the insulator shown in FIGo 3;
FIG. 6 is a view similar to FIG. 3 of another insulator embodying the present invention;
FIG. 7 is an enlarged view of the upper end of FIG. 6;
FIG. 8 is a front eleva~ional vie~ of still another insulator embodying the present invention, this embodiment being illustrated in FIGS. 1 and 2;
FIG. 9 is a side elevational view of FIG. 8~ and FIG. 10 is an enlarged view of the lower portion of FIG.
8.
Corresponding reference characters indicate corresponding parts:throughout ~he several views of the drawingS.
.
:~ :
86~
Description of Preferred EmbodimentS
Referring now to the drawings, an electrical resistance heater is generally indicated in it~ entire~y by reference character 1. Heater 1 includes a frame7 as generally indicated at 3, having side bars or rods 5 extending longitudinally of the f~ame and having ends 7 at each end thereof. As shown, frame 3 is constituted by a one-piece, formed rod and the frame has three support bars or pla~es 9 extending transversely between side members 5 for supporting the hea~ing element in a manner as will appear. Each of the support bars i8 of formed ~heet metal and is secured (e.g., welded) at its ends to side rods 5.
As generally indicated at 11, a heating element is mounted on the support bars 9 of frame 3 by means of insulators embodying the present invention (a description of which will appear in detail hereinafter). As is typical, heating element 11 ~s a continuous length of suitable electrical resistance heating wire, ,., c ~
such as ~P~shco;e or the like, and such as is well known to those skilled in the art. As shown, heating element 11 has a plurality (e.g., six) of heating element runs 13a-13f extending generally parallel to one another with three of the runs 13a-13c being located on one side of support bars 9 and with the other ~hree runs 13d-13f being locatsd on the other side of the support bars. As shown, each of the runs i8 constituted by a longitudinal helical coil of the electrical resistance heating wire with the coil having a multiplicity of generally uniformly spaced convolu~ions and having center helical coll axis, as indicated by A---A in ~IGS. 1-3.
_ g _ 6~ii Each of the ad~acent runs 13a-13f of the heatiny element 11 are electrically connected in series to an adjacent run o~ the heating element by meang of a so-called turnaround, as indica~ed at 15a-15e. More specifically, i~ will be noted that each oZ the turnarounds is not of helical coil construction, but rather each of tne turnarounds 15a-lSe has a defined length of heating element wire therein and each of the turnarounds includes a partially closed loop, as generally indicated at L~ electrically connecting the end of one heating element run te.9., run 13a~
with the end of the next adjacent run ~e.g., run 13b) in series therewith thereby to provide electrical con~inuity from one end of heating element 11 to the otherO
In addition to the helical coiled runs 13a-13b and the looped end turns lSa 15f, as above described, heating element 11 includes a pair of leads, a~ indicated at 17a, 17b, integral with the heating element and constituting the ends of heating element 11 with these leads being electrically connected ~4 respective electrical terminals l9a, l9b~ Those skilled in the art will recognize that the terminals l9a, l9b may be connected to a source of electrical power for energization of heating element 11 in the conventional manner. Further, frame 3 for heating element 1 comprises a terminal ~upport bracket 21. The ~upport bracket is carried by a plate 23 which is ~ecured to one end 7 of frame 3. Wi~hin the broader aspects of this invention, heater frame~
of other co~figurations may be used.
6~
As heretofore mentioned, runs 13a-13f of heating element 11 are supported on electrical and thermal insulator~, each o~
which is generally indicated a~ 25~ thereby ~o hold ~he heating elemen~ 11 clear of frame 3 and to support the heating element during energization. As shown best in FIG. 2, each insulator 25 is carried by a respec~ive support bar 9 and has the provision on both its upper and lower faces (as viewed in FIG. 2) of securing and supporting a respective run of heating element 11 in such manner as to maximize heat transfer from the convolu~ions of the heating element engageable with the insulator thereby to minimize tne operating temperature of the portions of the heating coil suppor~ed by the insulato~ and also so as to support the heating coil in such manner as to minimize sag of the helical coil heating element extending between the insulators.
As shown in FIG. 3, a first insulator 25 is shown to be generally symmetrical about an axis, or plane, as indicated by B---B and thus only the lower portion of the insulator, as shown in FIG~ 5, will be described in detail.
However, those skilled in the art will recognize tbat the bottom portion of the insulator is essentially identical and operates to support its respective heating element run in the same manner as will hereinafter be described. Further, while insulators 25 are herein shown and described a~ supportlny an upper and a lower coil, the insulators n~ed not be vertically oriented and may support the heater runs to the side o~ the heater 1, or at any other desired angle.
~v~
As is conven~ional, insulator 25 i8 preferably made of a ceramic-like material, for example cordierlte or steatite, 80 as to electrically insulate heating element 11 ~rom frame 3 and also so as to ~hermally insulate the heating element and to prevent undue conduction of heat away rom the portions of he heating e~lement in contact with the insulator.
Insulator 25 is constituted by a body 27 of the steatite material (or of other ceramic electrical insûlative material~
with the body having a width or thlcknes~ T, a~ shown in FIG. 4, and having an overall length, as indicated by dimension L in FIG.
Among the several objects and ~eatur~ of this disclosure may be noted tne provision of an insulator for an electrical resistance heater in which the insulators contact three adjacent convolutions of the helical coiled heating element at only localizea points therearound thereby to permit air circulation to flow freely over the convolutions supported by the insulators;
8~
The provision of such an insula~or in which the heating element may be ~ormed to i~s desired configuration and readily applied to the insulators already installed on t.he frame for the heating element;
The provision of such an insulator in which the heating cQil may be readily installed on the heating coil in such manner as to effect substantial labor ~avings in assembly of the heating element and, at least in certain instance~, to facilitate the automated installation of the heating coil~ on the insulators;
The provision of such an insulator which minimizes stretching of the heating element coil as the latter i~ installed on the insula~ors, and yet which in~ures that the heating coil is locked in place on the insulator~
The pravision of sucb an insulator which permits the ready field repair of the heating elemen~, even after ~he heating element has been ~ired, without undue breakage o~ the heating element;
The provision of such an insulator wbich support~ the runs of the heating element in 6uch manner as to lessen the tendency of:the heating element ~o sag; and The provision of such an insulator which is of simple and rugged construction, which i~ easy ~o assembly, which requires less labor to manu~acture, which has a longer service life, and which is more readily field repairable than prior heating elements. ~
Other objects and features of this invention will be in part poin~ed out and in paFt apparent hereinafter.
. - 5 -Briefly stated, an electrical resis~ance heater typically has an elongate wire heating elemen~ of generally helical coil shape. The helical coil has a coil axiz and a plurality of convolutions spaced at ~ubstantially equal intervals along the coil axis. The heater further has a frame and a plurality of electrical insula~ors for supporting the heating element on the frame. Each o~ the insula~ors has a unitary body of a suitable electrical insulative material. The body has a first and a second side facing in generally opposite directions.
Tne insulator includes means for mounting ~he insulator body with respect to the frame such that the first and second sides are generally in line with the coil axis. The insulator body further has a side notch in each of it~ above-mentioned ~r~t and second sides, with each of the side notches extending generally inwardly toward the center of the insulator body~ Further, at lea~t a portion of the first and second sides of the insulator body is spaced outwardly from the insulator body mounting means, and these portions angle inwardly so as to con~titute a pair of outer ~aces converging toward one another. The insulator ~urther has an outer end between the angled outer faces, with ths outer end of the insulator body having a center notch therein extending inwardly toward the moun~ing means. The ends of the in~ulator body between the outer ends of each of the angled outer faces and the outer end of its adjacent center no~ch face has a wid~h less than the axial spacing between the convolutions of the coil along the coil. ~his permits the ends of the insulator and the coil heating element to be assembLed by disposing the insulator relative to the coil with one convolution ~ub~tantially in register with the center notch, and with adjacent convolutions on Opposite sides of this one convolution being engageable with a respective angled outer face of the insulator body. By moving the insulator and coil toward one another, the one convolution i~
received within the center notch, and ~he adjacent convolutions are weagingly spread outwardly away from the one convolution generally along the coil axis by engagement with their respective anglea outer faces of the insulator body unti~ the adjacent convolutions are in register with and snap into their respective side notches. In this manner, the side notche~ positively hold their respective coil convolutions again~t movement toward and away from the insulator body and such that the cen~er notch hol~s its respec~ive coil convolutions against movement along the coil axis.
Further, this disclosure includes a method of installing such a coil-type heating element on an insulator, generally as above-described, in which one heating element convolution is inserted into the center notch of the insulator, and in which adjacent convolutions are brought into contact with the angled outer faces of the insulator body. Then, the heating element coil is shoved onto the insulator such that the outer angled faces of the insulator wedgingly spread the adjacent convolutions outwardly relative to the one convolution received in the center notch until such time as the adjacent convolutions are received in the side notches such that the side notches prevent movement o the heating coil toward and away from the insulator, and ~uch that the convolution received in the center notch permits movemen~ of the heating elemen~ in the direction o~ the axis of the heating element coil.
3 6;5 In the accompanying drawings which illustrate embodiments of the invention;
FIG. 1 is a top plan view of an elect~ical resistance heater assembly having a plurality of runs of a coiled heating element supported on a frame by a plurality of in~ulators;
FIG. 2 is a side elevational view of FIG. 1, showing the insulator of FIG. 8;
FIG. 3 is a front elevationa~ view o~ a ~irs~ insulator embodying the present invention;
FIG. 4 is a side elevational view of the insulator of FIG. 3;
FIG. 5 is an enlarged view of the lower portion of the insulator shown in FIGo 3;
FIG. 6 is a view similar to FIG. 3 of another insulator embodying the present invention;
FIG. 7 is an enlarged view of the upper end of FIG. 6;
FIG. 8 is a front eleva~ional vie~ of still another insulator embodying the present invention, this embodiment being illustrated in FIGS. 1 and 2;
FIG. 9 is a side elevational view of FIG. 8~ and FIG. 10 is an enlarged view of the lower portion of FIG.
8.
Corresponding reference characters indicate corresponding parts:throughout ~he several views of the drawingS.
.
:~ :
86~
Description of Preferred EmbodimentS
Referring now to the drawings, an electrical resistance heater is generally indicated in it~ entire~y by reference character 1. Heater 1 includes a frame7 as generally indicated at 3, having side bars or rods 5 extending longitudinally of the f~ame and having ends 7 at each end thereof. As shown, frame 3 is constituted by a one-piece, formed rod and the frame has three support bars or pla~es 9 extending transversely between side members 5 for supporting the hea~ing element in a manner as will appear. Each of the support bars i8 of formed ~heet metal and is secured (e.g., welded) at its ends to side rods 5.
As generally indicated at 11, a heating element is mounted on the support bars 9 of frame 3 by means of insulators embodying the present invention (a description of which will appear in detail hereinafter). As is typical, heating element 11 ~s a continuous length of suitable electrical resistance heating wire, ,., c ~
such as ~P~shco;e or the like, and such as is well known to those skilled in the art. As shown, heating element 11 has a plurality (e.g., six) of heating element runs 13a-13f extending generally parallel to one another with three of the runs 13a-13c being located on one side of support bars 9 and with the other ~hree runs 13d-13f being locatsd on the other side of the support bars. As shown, each of the runs i8 constituted by a longitudinal helical coil of the electrical resistance heating wire with the coil having a multiplicity of generally uniformly spaced convolu~ions and having center helical coll axis, as indicated by A---A in ~IGS. 1-3.
_ g _ 6~ii Each of the ad~acent runs 13a-13f of the heatiny element 11 are electrically connected in series to an adjacent run o~ the heating element by meang of a so-called turnaround, as indica~ed at 15a-15e. More specifically, i~ will be noted that each oZ the turnarounds is not of helical coil construction, but rather each of tne turnarounds 15a-lSe has a defined length of heating element wire therein and each of the turnarounds includes a partially closed loop, as generally indicated at L~ electrically connecting the end of one heating element run te.9., run 13a~
with the end of the next adjacent run ~e.g., run 13b) in series therewith thereby to provide electrical con~inuity from one end of heating element 11 to the otherO
In addition to the helical coiled runs 13a-13b and the looped end turns lSa 15f, as above described, heating element 11 includes a pair of leads, a~ indicated at 17a, 17b, integral with the heating element and constituting the ends of heating element 11 with these leads being electrically connected ~4 respective electrical terminals l9a, l9b~ Those skilled in the art will recognize that the terminals l9a, l9b may be connected to a source of electrical power for energization of heating element 11 in the conventional manner. Further, frame 3 for heating element 1 comprises a terminal ~upport bracket 21. The ~upport bracket is carried by a plate 23 which is ~ecured to one end 7 of frame 3. Wi~hin the broader aspects of this invention, heater frame~
of other co~figurations may be used.
6~
As heretofore mentioned, runs 13a-13f of heating element 11 are supported on electrical and thermal insulator~, each o~
which is generally indicated a~ 25~ thereby ~o hold ~he heating elemen~ 11 clear of frame 3 and to support the heating element during energization. As shown best in FIG. 2, each insulator 25 is carried by a respec~ive support bar 9 and has the provision on both its upper and lower faces (as viewed in FIG. 2) of securing and supporting a respective run of heating element 11 in such manner as to maximize heat transfer from the convolu~ions of the heating element engageable with the insulator thereby to minimize tne operating temperature of the portions of the heating coil suppor~ed by the insulato~ and also so as to support the heating coil in such manner as to minimize sag of the helical coil heating element extending between the insulators.
As shown in FIG. 3, a first insulator 25 is shown to be generally symmetrical about an axis, or plane, as indicated by B---B and thus only the lower portion of the insulator, as shown in FIG~ 5, will be described in detail.
However, those skilled in the art will recognize tbat the bottom portion of the insulator is essentially identical and operates to support its respective heating element run in the same manner as will hereinafter be described. Further, while insulators 25 are herein shown and described a~ supportlny an upper and a lower coil, the insulators n~ed not be vertically oriented and may support the heater runs to the side o~ the heater 1, or at any other desired angle.
~v~
As is conven~ional, insulator 25 i8 preferably made of a ceramic-like material, for example cordierlte or steatite, 80 as to electrically insulate heating element 11 ~rom frame 3 and also so as to ~hermally insulate the heating element and to prevent undue conduction of heat away rom the portions of he heating e~lement in contact with the insulator.
Insulator 25 is constituted by a body 27 of the steatite material (or of other ceramic electrical insûlative material~
with the body having a width or thlcknes~ T, a~ shown in FIG. 4, and having an overall length, as indicated by dimension L in FIG.
4. As shown in FIG. 3, insulator 25 has a first side 29 (i.e., tne right side as shown in FIG. 3) and a ~econd side, as indicated at 310 Further, the insulator has a top and a bottom side or end 33 intermediate the first and second sides.
First side 29 has a blind notch, as indicated at 35, provided therein and side 31 has a similar notch 37 therein. Further, ~he upper ox lower ends 33 of the insulator have an intermediate or center notch 39 therein. The width of notches 35 and 37 is somewhat wider than the thickness of electrical resistance heating wire 11. As ~hown in FIGS. 3 and 5, the inner ends 40 of each of the side notches 35 and 37 are generally perpendicularly offset from the generally horizontal entrance portions of the side notche~ and end portions 40 are formed in a radius 80 as to engage and ~upport only a segment o~ a respective convolut~on 41 ~r 43 of a respective run 13a-13f of heating element 11 in engagement with the in~ulator.
i5 As is best shown in FIG. 5, the portion of the convolutions 41 and 43 of the heating element runs received in notches 35 and 37 are generally coplanar, as indicated by axis C--C. In one insulator embodying this invention, -the bottom of center notch 39 is preferably (but not necessarily~
spaced outwardly of axis C--C o~ the ends of notches 35 and 37 by an offset distance, as indicated at X in FIG. 5. Thus, upon installing a respective heating element run 13a-13 on a respective insulator 25, in a manner as will be hereinafter described, a first convolution, as indicated at 45, i3 placed in its respective cen~er notch 39 such that the heating coil is bent along its helical axis ~--A wi~h the bottoms of the next adjacent intermediate convolutions 43 and 45 received in their respec~ive side notches 35 and 37. Thus, the bottoms of convolu~ions 41 and 43 are resiliently sprung downwardly (as shown in FIG. 5) and are restrained against further downward movement by the closed ends 40 of the inclined notches 35 and 37. ~owever, because o~ the offset distance X between the inner ends 40 of the blind notches 35 and 37 relative to the bottom of intermediate 810t 39 convolution 45 is displaced outwardly away from the center axi~
A---A of the helical heating coil by ~he off~et difference X such that a resilient restraining force is applied ~o the heli~al coil as it extends from one insulator 25 ~o the next adjacent heating element. This resilient force tends to hold the coiled heating element in place on insulators 25 regardless of the orientation of the heating element or the insula~ors. Those skilled in the art will appreciate that the offset of intermediate convolution 45 due to ~he offset distance X of the three slots applie~ a ss resilient restoring force to the heating element coil ~uch that after even repeated firing (or heating) of the heater coil, and that this restorative, resilient force tends to minimize sagging of the heating coil between adjacent insulators 25 thus eliminatin9 or lessening a primary cau~e of heating elemen~
failure, viz., excessi~e heating coil sag. Further, the coll i8 pOsitively prevented ~rom moving in axial direction with re~pect to insulator 25. ~owever, wi~hin the broader a~pect~ of this invention~ center notch 39 need not be axially of~et from the plane C --C of notch ends 35 and 37 and still ~he heating element coil will be positively restrained against axial movement relative to insulator 25.
As will be further appreciated by tho~e skilled in the art, because only a relatively short segment of each of the convolutions 41, 43, and 45 (see FIG. 5) is in contact with the insulator 25, because substantial air flow can still be directed over a considerable sur~ace area of the ~egment of the heating element in contact with the insulator, and further because of the heat conduction properties of the insulator, insulator 25 prevents or lessens undue temperature buildup in the portion of the heating element in contact with the insulator and thus prolongs service li~e o~ heating element llo Still further, insulator~ 25 are 80 constructed such that they may be readily inserted into ~upport bar~ 9, positively retained in their installed position, and further ~uch that the completely formed heating element 11 including helical coil runs 13a-13b and the turnarounds 15a-15e may be read~ly and efficiently installed on the insula~ors, one insulator at a time~
4~
without the necessity of having to thread the heating element through the insulatorz as was her~ofore conventional when collar type insulators were used.
More partlsularly, ~uch insulator 25 (see FIG. 3) is shown to have a pair of notches 47 in its irgt and second sides 29 and 31 generally coincident wi~h symmetrical axis B---B, the inner bases of these notches being spaced apart from one another by a length, as indicated by dimens~on L~. Further, as shown in FIG. 1, each o the support bar~ 9 of frame 3 has a plurality of apertures (e.g., threel, as generally indicated by reference characters 49a-49b, one aperture for each insulator 25 to be carried by the support bar. More speci~ically, each aperture is identical and thus only aperture 49a, as illùstrated in FIG. 1, will be described in detail. Specifically, aperture 49a ~s shown to have a generally circular opening with a pair of dlametrically opposed rectangular notches 51a-51b. ~urther, a stop 53 is optionally provided within the generally circular aperture. It will be understood that the outer extremitles of notches 51a, 51b are spaced apart by a dimension W (see FIG. 1) which is somewhat larger than the overall width of insulator 25 between ~ide faces 27 and 29. The width of the ~lo~s 51a, 51b is somewhat wider than the thickness T of the insulator such that the insulator may be inserted freely through notches 51a, 51b and into aperture 49. With the insulator inserted approximately halfway through the aperture 49, as it appears in FIG. 2, the insulator may be rotated in counterclockwise direction (as viewed in FIG. 1) such that slots 47 in the sides of the i~sulator will receive the portion of support bar 9 defining the circular portion of aperture 49 ~hereby to prevent up and down movement (as viewed in FIGS. 2 and 3) of the insulator r~lative to the support bar.
Upon rotating the insulator in counterclockwise directlon approximately 90 to assume the po~ition of the in~ulator shown in FIG. 1, one face of the insula~or will engage stop 53 thereby properly aligning the insulator with respect to the support bars, such that side ~aces 29 and 31 of the insulator face in the direction of coil axis A--A. It will be apprec~ated ln thi~
manner, insulators 25 may readily be inserted into thP frame and secured in place without even the requirement of simple handtools. As thus far described, insulator 25 i8 similar to the insulator described in my co-assigned U.S. patent 4,472,624.
Referring now to FIGS. 3-5, insulator 25 is shown to have a pair of angled outer faces 55 and 57 at each end thereof, spaced outwardly from mountins notches 47, with these angled outer faces converging ~nwardly~ While in the emDodiments shown in FIGS. 3 5 the angled outer faces 55 and 57 are spaced outwardly from mounting notches 47, it will be understood that within the broa~er aspects of this disclosure, the length of ~ide faces 29 and 31 may vary considerably, or may even be eliminatedO Further, in outer end 33 of insulator body 27, center notch 39, as heretofore descr~bed, is defined by a pair of tapered center notch faces 59 and 61. Re~pective outer ~nd tips 63 and 65 are provided between angled oute~ ~ace 55 and center notch face 59, and between angled outer face 57 and center notch face 61 such that the center notch ~aces 59 and 61 converge inwardly toward the base of center notch 39, and sueh that the outer end tips 63 and 65 are radiused. It will be appreciated ` ~ Z~865 that the width of the outer end tips 63 and 65 is such that the width of the outer end tips i8 le88 ~han the normal spacing between adjacent convolutlon~ of the colled heating element.
Preferably, the distance beteen tips 63 and 65 and ~he ends of notch portions 40 is somewhat greater than half the diameter of the coil.
In accordance with the method here described insulators 25 are installed on hea~er frame 3 in the manner heretofore described such that the in~ulators are in their retained positions (as shown in F~G. 1l. Runs 13a-13f of heating element 11 are brought into position relative to insulators 25 such that a first convolution 45 of the heating element i8 generally in register with center notch 39 o~ a respective insulator 25, and such that adjacent convolutions 41 and 43 have a respective outer end tip 63 or 65 inser~ed, at least ~n p~rt, between convolutions 41 and 45, and be~ween convolutions 45 and 43, with the convolutions 41 and 43 engaging their respective angled ou~er faces 55 and 57. Then, the heating element coil is moved inwardly toward ~he b~se of center notch 39 (i e., toward axis B--B~, such that convolution 45 i8 received within the center notch, and such that angled outer faces 55 and 57 wedgin~ly spread their respective convolutions 41 and 43 in axial direction along coil axi~ A--A away from convolutiqn 45 received in center notch 31. As convolutions 41 and 43 move along angled outer faces 55 and 57 and move into regi~ter with side notches 35 and 37, the convolutions 41 and 43 snap into place within notche~
35 and 37. In this manner, the heating element coil is readily installed on and i~ positively re~ained on insulators 25 without special tools and without the necessity of manipula~ing the coil.
~2~ 5 Referring now to ~IGS. 6 and 7, a second embodiment of the insulator of the present invention i8 indlcated in its entirety by re~erence character 25'. ~t will be understood that the ~primed~ reference characters in FIGS. 6 and 7 indicate portions of the unitary insulator 25~ having a similar construction and ~unction as portions of insulator 25, as shown in FIGS 3-5 heretofore explained. Thus, for the sake of brevity, a detailed description of the cons~ruction and the function of these corresponding structural ~eatures of insulator 25' will not be herein set forth. The chief difference between insulator 25 and insulator 25~ resides primarily in the overall length of the insulators (insulator 25' is shown to be ~omewhat shorter tnan insulator 25), and in the ~ac~ that side notches 35' and 37' have two offset inner notch portions, as indicated at 40'a, 40'b, which extend toward the outer end 33 of the insulator, and toward the center o~ the insulator. It will be understood that by providing these two inner notch portions 40'a, 40'b, that the heating element convolutions 41 and 43 received in these side slots 35', 37', are prevented from moving in axial direction, botn toward and away from the ends 33' of the insulator body.
Referring no~ to FIGS. 8-10, still another insulator embodying the present invention (as shown in FIGS. 1 and 2) is indicated in its entirety by reference character 25~. It will be understood that the ~double primed~ re~erenae characterS
in FIGS. 8-10 have a corresponding construction and function to corresponding cons~ructions shown in FIGS. 3-7. The primary difference between insulator 25~ and insulator 25 and 25' i8 that ~.2~
the overall length of insulator 25n is considerably shorter such that the first and second sides 27~ and 29~ are con~iderablY
shorter, almost to the point that the first and ~econd sides are nonexistent. Additionally, as fihown in FIG. 10, side ~lots 35 and 37" each have an intermediate portion, as indicat2d at 38~, w~hich leads inwardly and downwardly (i.e., toward axis Bn--Bn~
and thence to notch end 40"). This intermediate notch portion 38" aids in holding coil convolutions 41 and 43 in place within side notches 35~ and 37". It will also be noted that notches 35"
and 37~ are, in fact~ incorpora~ed in respective angled side faces 55" and 57~ rather than in the side faces 27~ and 2g~
~ owever, installation of insulators 25~ and 25~ within frame 3 is essentially identical as above-described in regard to insulator 25. Further, ins~alla~ion of the heating element coi}
on the insulators 25' and 25~ is essentially the same as heretofore described.
In view of tne above, it will be ~een that the other objects of this invention are achieved and other advantayeous results obtained.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
First side 29 has a blind notch, as indicated at 35, provided therein and side 31 has a similar notch 37 therein. Further, ~he upper ox lower ends 33 of the insulator have an intermediate or center notch 39 therein. The width of notches 35 and 37 is somewhat wider than the thickness of electrical resistance heating wire 11. As ~hown in FIGS. 3 and 5, the inner ends 40 of each of the side notches 35 and 37 are generally perpendicularly offset from the generally horizontal entrance portions of the side notche~ and end portions 40 are formed in a radius 80 as to engage and ~upport only a segment o~ a respective convolut~on 41 ~r 43 of a respective run 13a-13f of heating element 11 in engagement with the in~ulator.
i5 As is best shown in FIG. 5, the portion of the convolutions 41 and 43 of the heating element runs received in notches 35 and 37 are generally coplanar, as indicated by axis C--C. In one insulator embodying this invention, -the bottom of center notch 39 is preferably (but not necessarily~
spaced outwardly of axis C--C o~ the ends of notches 35 and 37 by an offset distance, as indicated at X in FIG. 5. Thus, upon installing a respective heating element run 13a-13 on a respective insulator 25, in a manner as will be hereinafter described, a first convolution, as indicated at 45, i3 placed in its respective cen~er notch 39 such that the heating coil is bent along its helical axis ~--A wi~h the bottoms of the next adjacent intermediate convolutions 43 and 45 received in their respec~ive side notches 35 and 37. Thus, the bottoms of convolu~ions 41 and 43 are resiliently sprung downwardly (as shown in FIG. 5) and are restrained against further downward movement by the closed ends 40 of the inclined notches 35 and 37. ~owever, because o~ the offset distance X between the inner ends 40 of the blind notches 35 and 37 relative to the bottom of intermediate 810t 39 convolution 45 is displaced outwardly away from the center axi~
A---A of the helical heating coil by ~he off~et difference X such that a resilient restraining force is applied ~o the heli~al coil as it extends from one insulator 25 ~o the next adjacent heating element. This resilient force tends to hold the coiled heating element in place on insulators 25 regardless of the orientation of the heating element or the insula~ors. Those skilled in the art will appreciate that the offset of intermediate convolution 45 due to ~he offset distance X of the three slots applie~ a ss resilient restoring force to the heating element coil ~uch that after even repeated firing (or heating) of the heater coil, and that this restorative, resilient force tends to minimize sagging of the heating coil between adjacent insulators 25 thus eliminatin9 or lessening a primary cau~e of heating elemen~
failure, viz., excessi~e heating coil sag. Further, the coll i8 pOsitively prevented ~rom moving in axial direction with re~pect to insulator 25. ~owever, wi~hin the broader a~pect~ of this invention~ center notch 39 need not be axially of~et from the plane C --C of notch ends 35 and 37 and still ~he heating element coil will be positively restrained against axial movement relative to insulator 25.
As will be further appreciated by tho~e skilled in the art, because only a relatively short segment of each of the convolutions 41, 43, and 45 (see FIG. 5) is in contact with the insulator 25, because substantial air flow can still be directed over a considerable sur~ace area of the ~egment of the heating element in contact with the insulator, and further because of the heat conduction properties of the insulator, insulator 25 prevents or lessens undue temperature buildup in the portion of the heating element in contact with the insulator and thus prolongs service li~e o~ heating element llo Still further, insulator~ 25 are 80 constructed such that they may be readily inserted into ~upport bar~ 9, positively retained in their installed position, and further ~uch that the completely formed heating element 11 including helical coil runs 13a-13b and the turnarounds 15a-15e may be read~ly and efficiently installed on the insula~ors, one insulator at a time~
4~
without the necessity of having to thread the heating element through the insulatorz as was her~ofore conventional when collar type insulators were used.
More partlsularly, ~uch insulator 25 (see FIG. 3) is shown to have a pair of notches 47 in its irgt and second sides 29 and 31 generally coincident wi~h symmetrical axis B---B, the inner bases of these notches being spaced apart from one another by a length, as indicated by dimens~on L~. Further, as shown in FIG. 1, each o the support bar~ 9 of frame 3 has a plurality of apertures (e.g., threel, as generally indicated by reference characters 49a-49b, one aperture for each insulator 25 to be carried by the support bar. More speci~ically, each aperture is identical and thus only aperture 49a, as illùstrated in FIG. 1, will be described in detail. Specifically, aperture 49a ~s shown to have a generally circular opening with a pair of dlametrically opposed rectangular notches 51a-51b. ~urther, a stop 53 is optionally provided within the generally circular aperture. It will be understood that the outer extremitles of notches 51a, 51b are spaced apart by a dimension W (see FIG. 1) which is somewhat larger than the overall width of insulator 25 between ~ide faces 27 and 29. The width of the ~lo~s 51a, 51b is somewhat wider than the thickness T of the insulator such that the insulator may be inserted freely through notches 51a, 51b and into aperture 49. With the insulator inserted approximately halfway through the aperture 49, as it appears in FIG. 2, the insulator may be rotated in counterclockwise direction (as viewed in FIG. 1) such that slots 47 in the sides of the i~sulator will receive the portion of support bar 9 defining the circular portion of aperture 49 ~hereby to prevent up and down movement (as viewed in FIGS. 2 and 3) of the insulator r~lative to the support bar.
Upon rotating the insulator in counterclockwise directlon approximately 90 to assume the po~ition of the in~ulator shown in FIG. 1, one face of the insula~or will engage stop 53 thereby properly aligning the insulator with respect to the support bars, such that side ~aces 29 and 31 of the insulator face in the direction of coil axis A--A. It will be apprec~ated ln thi~
manner, insulators 25 may readily be inserted into thP frame and secured in place without even the requirement of simple handtools. As thus far described, insulator 25 i8 similar to the insulator described in my co-assigned U.S. patent 4,472,624.
Referring now to FIGS. 3-5, insulator 25 is shown to have a pair of angled outer faces 55 and 57 at each end thereof, spaced outwardly from mountins notches 47, with these angled outer faces converging ~nwardly~ While in the emDodiments shown in FIGS. 3 5 the angled outer faces 55 and 57 are spaced outwardly from mounting notches 47, it will be understood that within the broa~er aspects of this disclosure, the length of ~ide faces 29 and 31 may vary considerably, or may even be eliminatedO Further, in outer end 33 of insulator body 27, center notch 39, as heretofore descr~bed, is defined by a pair of tapered center notch faces 59 and 61. Re~pective outer ~nd tips 63 and 65 are provided between angled oute~ ~ace 55 and center notch face 59, and between angled outer face 57 and center notch face 61 such that the center notch ~aces 59 and 61 converge inwardly toward the base of center notch 39, and sueh that the outer end tips 63 and 65 are radiused. It will be appreciated ` ~ Z~865 that the width of the outer end tips 63 and 65 is such that the width of the outer end tips i8 le88 ~han the normal spacing between adjacent convolutlon~ of the colled heating element.
Preferably, the distance beteen tips 63 and 65 and ~he ends of notch portions 40 is somewhat greater than half the diameter of the coil.
In accordance with the method here described insulators 25 are installed on hea~er frame 3 in the manner heretofore described such that the in~ulators are in their retained positions (as shown in F~G. 1l. Runs 13a-13f of heating element 11 are brought into position relative to insulators 25 such that a first convolution 45 of the heating element i8 generally in register with center notch 39 o~ a respective insulator 25, and such that adjacent convolutions 41 and 43 have a respective outer end tip 63 or 65 inser~ed, at least ~n p~rt, between convolutions 41 and 45, and be~ween convolutions 45 and 43, with the convolutions 41 and 43 engaging their respective angled ou~er faces 55 and 57. Then, the heating element coil is moved inwardly toward ~he b~se of center notch 39 (i e., toward axis B--B~, such that convolution 45 i8 received within the center notch, and such that angled outer faces 55 and 57 wedgin~ly spread their respective convolutions 41 and 43 in axial direction along coil axi~ A--A away from convolutiqn 45 received in center notch 31. As convolutions 41 and 43 move along angled outer faces 55 and 57 and move into regi~ter with side notches 35 and 37, the convolutions 41 and 43 snap into place within notche~
35 and 37. In this manner, the heating element coil is readily installed on and i~ positively re~ained on insulators 25 without special tools and without the necessity of manipula~ing the coil.
~2~ 5 Referring now to ~IGS. 6 and 7, a second embodiment of the insulator of the present invention i8 indlcated in its entirety by re~erence character 25'. ~t will be understood that the ~primed~ reference characters in FIGS. 6 and 7 indicate portions of the unitary insulator 25~ having a similar construction and ~unction as portions of insulator 25, as shown in FIGS 3-5 heretofore explained. Thus, for the sake of brevity, a detailed description of the cons~ruction and the function of these corresponding structural ~eatures of insulator 25' will not be herein set forth. The chief difference between insulator 25 and insulator 25~ resides primarily in the overall length of the insulators (insulator 25' is shown to be ~omewhat shorter tnan insulator 25), and in the ~ac~ that side notches 35' and 37' have two offset inner notch portions, as indicated at 40'a, 40'b, which extend toward the outer end 33 of the insulator, and toward the center o~ the insulator. It will be understood that by providing these two inner notch portions 40'a, 40'b, that the heating element convolutions 41 and 43 received in these side slots 35', 37', are prevented from moving in axial direction, botn toward and away from the ends 33' of the insulator body.
Referring no~ to FIGS. 8-10, still another insulator embodying the present invention (as shown in FIGS. 1 and 2) is indicated in its entirety by reference character 25~. It will be understood that the ~double primed~ re~erenae characterS
in FIGS. 8-10 have a corresponding construction and function to corresponding cons~ructions shown in FIGS. 3-7. The primary difference between insulator 25~ and insulator 25 and 25' i8 that ~.2~
the overall length of insulator 25n is considerably shorter such that the first and second sides 27~ and 29~ are con~iderablY
shorter, almost to the point that the first and ~econd sides are nonexistent. Additionally, as fihown in FIG. 10, side ~lots 35 and 37" each have an intermediate portion, as indicat2d at 38~, w~hich leads inwardly and downwardly (i.e., toward axis Bn--Bn~
and thence to notch end 40"). This intermediate notch portion 38" aids in holding coil convolutions 41 and 43 in place within side notches 35~ and 37". It will also be noted that notches 35"
and 37~ are, in fact~ incorpora~ed in respective angled side faces 55" and 57~ rather than in the side faces 27~ and 2g~
~ owever, installation of insulators 25~ and 25~ within frame 3 is essentially identical as above-described in regard to insulator 25. Further, ins~alla~ion of the heating element coi}
on the insulators 25' and 25~ is essentially the same as heretofore described.
In view of tne above, it will be ~een that the other objects of this invention are achieved and other advantayeous results obtained.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an electrical resistance heater having an elongate wire heating element of generally helical coil construction, said coil having a coil axis and a plurality of convolutions spaced at substantially equal intervals along said coil axis, said heater having a frame and a plurality of electrical insulators supporting said heating element on said frame, wherein the improvement comprises: each of said insulators having a unitary body of a suitable electrical insulative material, said body having a first and a second side facing in generally opposite direction, means for mounting said insulator body with respect to said frame such that said first and second sides of said insulator body are generally in line with said coil axis, said insulator body having a side notch in each of its said first and second sides, each of said side notches extending generally inwardly toward the center of said insulator body and having in inner end, at least a portion of said first and second sides of said insulator body being substantially planar and spaced outwardly with respect to said frame from said mounting means and angling inwardly 50 as to constitute a pair of planar, angled outer faces converging toward one another, said insulator body having an outer end between said angled outer faces, said outer end having a pair of inwardly converging, planar center notch faces defining a center notch extending inwardly toward said mounting means, means for wedgingly expanding said coil upon installation of said coil on said insulator, this last said means comprising a pair of body end portions or tips between the outer ends of each of said planar, angled outer faces and the outer end of its adjacent said planar center notch face with the distance between said center notch and each of said tips being less than the axial spacing of said convolutions along said coil axis when said coil is substantially unstretched so as to permit said insulator body and said coil to be assembled by disposing said insulator body relative to said coil with said first and second sides of said insulator body facing in opposite directions with respect to said coil axis, with one convolution of said coil substantially in register with said center notch, and with adjacent convolutions of said coil on opposite sides of said one convolution being disposed for wedging engagement by respective said planar angled outer faces of said insulator body such that said one convolution is received within said center notch and such that each of said tips is disposed between said one convolution and a next adjacent convolution so that said next adjacent convolutions are wedgingly spread outwardly away from said one convolution by engagement with a respective said planar angled outer face until said next adjacent convolutions are in register with and are received in said side notches, and means for positively retaining said coil in position on said insulator including said center notch having a base which is offset relative to said coil axis with respect to a line established by the inner ends of said side notches and further including each of said side notches having a first or entry portion extending generally inwardly of the insulator from the respective fir&t or second side thereof and a second or end portion at an angle with respect to said entry portion and extending toward said outer end of said insulator thereby defining a retaining shoulder between said entry and end portion of said slot so as to positively prevent said coil convolutions received in said side slots from exiting said side slots.
2. In an electric heater as set forth in claim 1 wherein said pair of angled outer faces converging toward one anther having an included angle therebetween ranging between about 30-60 degrees.
3. In an electric heater as set forth in claim Z wherein said included angle is about 50 degrees.
4. In an electric heater as set forth in claim 1 wherein the included angle between said center notch faces ranges between about 10 and 30 degrees.
5. In an electric heater as set forth in claim 4 wherein said included angle between said center notch faces is about 15 degrees.
6. In an electric heater as set forth in claim 1 further comprising a tip between each of said angled outer faces and a respective adjacent center notch face, and wherein the length of said insulator between said body portion tip and a respective said side notch is greater than one-half of the diameter of said coil.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US700,116 | 1985-02-11 | ||
| US06/700,116 US4628189A (en) | 1985-02-11 | 1985-02-11 | Electric resistance heater |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1244865A true CA1244865A (en) | 1988-11-15 |
Family
ID=24812255
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000490314A Expired CA1244865A (en) | 1985-02-11 | 1985-09-10 | Insulator for and method of installing electric resistance heater |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4628189A (en) |
| CA (1) | CA1244865A (en) |
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| US9386634B2 (en) * | 2011-04-15 | 2016-07-05 | Tutco, Inc. | Electrical resistance heater assembly and method of use |
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| US9095004B2 (en) | 2012-09-10 | 2015-07-28 | Tutco, Inc. | Insulator for open coil electrical resistance heater, heater using same, and method of use |
| US9234674B2 (en) * | 2012-12-21 | 2016-01-12 | Eemax, Inc. | Next generation bare wire water heater |
| DE202020101182U1 (en) * | 2020-03-04 | 2020-03-12 | Türk & Hillinger GmbH | Electric heater |
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| US2921172A (en) * | 1957-03-26 | 1960-01-12 | Tuttle Electric Products Inc | Open coil electric heater |
| US3016441A (en) * | 1960-05-23 | 1962-01-09 | Tuttle Electric Products Inc | Split strap supporting means for electrical insulators |
| US3358074A (en) * | 1965-06-02 | 1967-12-12 | Wagner E R Mfg Co | Insulator-frame arrangement for an electric heater |
| US3641312A (en) * | 1970-06-23 | 1972-02-08 | Heatcraft | Open coil heating element assembly |
| US3697727A (en) * | 1970-07-02 | 1972-10-10 | Ohio Decorative Products Inc | Open coil electric heater |
| US3770939A (en) * | 1972-09-19 | 1973-11-06 | Emerson Electric Co | Electric heating assemblies |
| US3846619A (en) * | 1973-11-12 | 1974-11-05 | Emerson Electric Co | Open coil electric heater |
| US3890487A (en) * | 1974-03-04 | 1975-06-17 | Emerson Electric Co | Open coil heater having spaced end coils |
| US3883721A (en) * | 1974-03-20 | 1975-05-13 | Emerson Electric Co | Open coil electric heater assembly |
| US3943333A (en) * | 1974-08-23 | 1976-03-09 | Kokjohn Leonard D | Open coil electric heating elements |
| US4144445A (en) * | 1977-12-27 | 1979-03-13 | Emerson Electric Co. | Open coil electric heaters |
| US4250399A (en) * | 1979-01-22 | 1981-02-10 | Emerson Electric Co. | Electric heating elements |
| US4268742A (en) * | 1979-10-17 | 1981-05-19 | E. R. Wagner Manufacturing Company | Resistance heater assembly |
| US4458141A (en) * | 1980-11-14 | 1984-07-03 | Tutco, Inc. | Electric heater and coil support insulator therefor |
| US4363959A (en) * | 1981-08-31 | 1982-12-14 | E. R. Wagner Manufacturing Company | Stand-off for resistance wires |
| US4472624A (en) * | 1982-06-10 | 1984-09-18 | Emerson Electric Co. | Electric resistance heater |
| US4531017A (en) * | 1983-11-25 | 1985-07-23 | Tutco, Inc. | Insulator for an electric heater |
| US4481411A (en) * | 1983-12-21 | 1984-11-06 | Intertherm Inc. | Electrical heater rack assembly with stand-off insulators |
-
1985
- 1985-02-11 US US06/700,116 patent/US4628189A/en not_active Expired - Fee Related
- 1985-09-10 CA CA000490314A patent/CA1244865A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4628189A (en) | 1986-12-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |